Microwave energy having a frequency between 14 GHz and 15 GHz can produce controlled ablation of biological tissue. At these frequencies, the depth of penetration of the radiation is limited, which may be beneficial.
WO 2004/047659 and WO 2005/115235 disclose apparatus for and methods of both ablating tissue and measuring information about tissue type and/or state using microwave radiation. These documents disclose the benefits of performing dynamic impedance matching between the energy source and the tissue.
These documents address the disadvantage of using RF and low frequency microwave treatment systems, where the dominant energy transport mechanism is thermal conduction and the depth of penetration (defined herein as being the distance the energy has spread when the energy source has reduced to 37% of the maximum value) is such that a large mass of tissue is heated before the temperature of the target tissue can be elevated to the required value.